Latency is the delay between asking a system for something and getting the first part of the answer back. It is usually measured in milliseconds, and on the web it covers the round trip a request makes from a user’s device to the server and back. Low latency feels instant. High latency feels like waiting.
A useful comparison is ordering food at a counter. Latency is the gap between placing your order and the kitchen acknowledging it, not how big the meal is. Even a small request feels slow if the kitchen is far away or busy. Distance is a big factor, which is why content served from a network of servers close to your users responds faster, and why heavy network traffic can push delays up during peak times.
It helps to separate latency from bandwidth, because people often blame the wrong one. Bandwidth is how wide the pipe is; latency is how long the journey takes. You can have a fast connection that still feels sluggish if every request has to travel to a server on another continent. Adding more bandwidth does nothing for that, only shortening the distance does.
Latency matters more than people expect. A page that takes an extra second to respond can lose real visitors and sales, and in apps like video calls or trading, even tens of milliseconds count. The fixes that work are practical: cache common responses so they never hit the database, and cut the number of separate round trips a single page needs, since each one adds its own delay.
At TopDevs we measure latency as a normal part of monitoring, and we place caching and servers where they shave off the delays that users actually feel.
